Getting the Right Power: 15 PC Power Supply Units


This special device is used to simulate the power consumption of a PC system

The performance capacity of the power supply unit is measured with a special measurement platform: the power consumption of typical components in a PC is simulated with resistive loads. When the resistance applied to +3.3-, + 5- and +12-volt lines is reduced, the power consumption and thus energy use increase when output power remains constant. The basis of the power test is the power that the PC components of a high-end system cause the strands of the +3.3-, + 5- and +12-volt power bus to use, expressed in percentage values.

Components +3.3 Volt +5.0 Volt +12.0 Volt Number Achievement
Processor AMD Athlon XP 3000+. 1.65 V 7.73 A 1 92.76 W
Mainboard and onboard-devices 3.00 A 2.00 A 0.30 A 1 23.50 W
System Fan 0.25 A 1 3.00 W
CPU-fan 0.25 A 1 3.00 W
Memory-module and -electronics(128 MByte DDR-DIMM) 2.00 A 4 40.00 W
AGP-Graphic Card 6.00 A 2.00 A 1 29.80 W
PCI-Modem 0.50 A 1 2.50 W
PCI-Sound 0.50 A 0.50 A 1 4.15 W
PCI-LAN 0.40 A 0.40 A 1 3.32 W
IDE-Hard Drive 0.80 A 2.00 A 4 112.00 W
DVD-Drive 0.65 A 0.85 A 1 13.45 W
DVD-R/RW-Drive 0.85 A 0.75 A 1 13.25 W
Floppy 0.80 A 1 4.00 W
USB-Devices 0.50 A 2 5.00 W
IEEE 1394 1.60 A 1 8.00 W
Keyboard 0.25 A 1 1.25 W
Mouse 0.25 A 1 1.25 W
Total Power Consumption 32.67 W 110.00 W 217.56 W 360.23 W
In a high-end system, power spikes of over 350 watts can occur

These values are used to calculate the ratio of the load on individual strands. What is being measured is whether the power supplies keep the operating voltages within the range of specifications. To allow better comparison of products in different power classes, the measurement is taken at the following power levels: 300, 350, 400 and 450 watts, depending on the power class of the candidates.

The maximum power of the power supply units - regardless of manufacturers' specifications - is also being measured. This maximum load is an index for the capacity and quality of the components being used.

Also relevant to the rating is the efficiency factor - the ratio of input power to output power. Another important element in the rating of power supplies is operating noise. The volume is determined with a sound level meter shortly after power-up at low capacity and at high temperatures at full capacity.

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